1. Field of the Invention
This invention relates generally to throttles for controlling flow through intake systems of internal combustion engines, and more specifically to two forms of throttle bodies, one having both a mechanically actuated throttle blade and an idle air control valve, and the other having an electric motor actuator for the throttle blade.
2. Background Information, Including Reference To Related Patent Applications And Incorporation By Reference
Spark-ignited, fuel-injected internal combustion engines enjoy extensive usage as the powerplants of automotive vehicles. A representative intake system for such an engine comprises a throttle body that has a through-bore within which a throttle blade, or throttle plate, also sometimes referred to as a butterfly, is disposed. The throttle blade is fastened to a cylindrical shaft whose axis is substantially coincident with a diameter of the through-bore. The shaft is journaled on opposite wall portions of the throttle body for motion about its own axis. An actuator that is external to the through-bore selectively positions the shaft about its own axis, to thereby selectively position the throttle blade within the through-bore over a range of positions spanning a closed throttle position and a full open throttle position.
One type of actuator for operating the throttle of an automotive vehicle is a strictly mechanical device that is direct operated by the driver's depressing of an accelerator pedal. For example, motion of the accelerator pedal may be transmitted through a sheathed cable to a lever, or cam, that is disposed on the throttle shaft external to the throttle through-bore. If that vehicle is also equipped with a cruise control system, the cruise control input is from a servo, or the like, which is remote from the throttle, but still cable-coupled to the throttle cam, or lever. The throttle body has a by-pass passage that parallels that portion of the through-bore containing the throttle blade. When the throttle blade is in closed position and the engine is idling, an idle air control valve meters intake air flow through the by-pass passage, thereby controlling the airflow into the engine past the closed throttle blade.
Another type of actuator is electromechanical in nature. An example is an electric (or electronic) throttle control, or ETC, in which the shaft of an electric motor is coupled to the throttle shaft through some form of coupling mechanism. The throttle blade is positioned by rotary motion of the motor shaft. The motor is itself controlled by an electronic controller, such as an engine management computer for example, in accordance with a signal from a sensor that is operated by the accelerator pedal. The controller essentially slaves the throttle to the pedal so that the blade is operated to a position corresponding to the position of the pedal. A cruise control system may be conveniently integrated with an electronic throttle control without a servo because of the presence of the electric motor that operates the throttle shaft. In known ETC systems, the motor is external to the throttle body and its shaft is coupled to the throttle shaft by a mechanical coupling. A gear train that provides gear reduction is one example of such a coupling.
Commonly owned, co-pending U.S. patent application Ser. No. 09/050,183 discloses a Clamshell Throttle Body Assembly. That throttle body comprises two body halves that meet face-to-face at a common mating plane that is perpendicular to a central longitudinal axis of the throttle body that coincides with that of a central circular through-bore of the throttle body. Before the two body halves are assembled together, a throttle mechanism comprising a circular throttle blade of uniform thickness disposed on a throttle shaft is placed between the two faces. As the two halves are moved together to place their mutually confronting faces on the common mating plane, circular bearing assemblies disposed on the shaft to either side of the blade become captured in shouldered circular apertures at diametrically opposite portions of the through-bore wall. As a result, the throttle blade is disposed within the through-bore for positioning about the shaft axis via low-friction journals on opposite wall portions of the through-bore.
Proximate the common mating plane, the through-bore wall comprises two generally semi-circular ledges, one in one throttle body half and the other in the other throttle body half. Each ledge is spaced from the common mating plane a distance essentially equal to one-half the thickness of the throttle blade. One ledge occupies essentially one semi-circumference of the throttle body, and the other, essentially an opposite semi-circumference. When the throttle blade is in closed position, it assumes an orientation that is perpendicular to the through-bore axis, with opposite semi-circular margins of its circular perimeter being disposed essentially flat against the opposite semi-circular ledges.
Other commonly-owned pending patent applications that relate to further improvements in Clamshell Throttle Body Assemblies are: THROTTLE BODY MODULE HAVING IMPROVED BLADE TO LEDGE SEALING Ser. No. 09/260,331, relating to improved sealing of a closed throttle blade to one of the two ledges in the throttle body through-bore; THROTTLE BODY MODULE HAVING IMPROVED FLUID TIGHTNESS Ser. No. 09/260,201, relating to novel gasket sealing between confronting faces of the two halves of the clamshell, including sealing proximate the bearing assemblies of the throttle mechanism; and INTEGRATED THROTTLE BODY AND INTAKE MANIFOLD SPACER MODULE Ser. No. 09/260,323, relating to certain constructional aspects of the module, its throttle body, and its throttle mechanism.
The entire content of each of the four other commonly owned pending applications mentioned above is expressly incorporated herein by reference as if fully disclosed herein.